Fuel injection pump for diesel type engines



Nov. 10, 1942. SCHWElTZER 2,301,464

FUEL INJECTION PUMP FOR DIESEL TYPE ENGINES Filed NOV. 9, 1940 20 14 1.6if 25 14 1.3 22 '13 16 18 21 164 1? i7 17 J&\ M J 6% J it I it i i I 4--Z HHHHII gimm mum 1 1 HLHJZ I I IE9 E l A;

, INVENTOR.

Q2 H.- W/TN 6656. MW BY 93, Mr 54 5 0 N ATTORNEYS.

Patented Nov. 10, 1942 UNITED STATES PATENT OFFICE FUEL INJECTION 1 2x20]; DIESEL TYPE Paul H. Schweitzer, State The Pennsylvania ResearchCollege, Pa, assignor to Corporation, State College, Pa., a corporationof Pennsylvania Application November 9, 1940, Serial No. 365,125

6 Claims.

This invention relates to port-controlled fuelinjection jerk pumps forinternal combustion engines of the Diesel type, and particularly forengines of that typethat are used for driving various kinds of vehicles,such as automobiles, trucks, airplanes and the like.

The quantity of fuel injected per cycle by such pumps is usuallycontrolled by a rod, but it is well known that with a fixed setting ofthe control rod the metering of fuel by a pump increases with increasingspeed of the pump, which results in.

an undesirable smoky exhaust. It also results in unstable engineoperation and a tendency to stall because a decrease in engine speedcaused by a sudden increase in load resistance produces reducedinjection and so further reduces the speed of the vehicle until itstalls. The reason usually ascribed to this increased metering of fuelat increased speed is that the delivery of fuel into the discharge tubeleading from a pump occurs earlier and its termination takes place laterbecause of a throttling action in the inlet and by-pass ports of thepump. For maximum torque and to avoid a smoky exhaust and also forengine stability it is desirable, with a fixed setting of the controlrod, to deliver a decreasing amount of fuel with increasing speed, whichis generally designated as a declining characteristic of fuel delivery.While various expedients have been proposed, and some have been used,for effecting a declining characteristic of fuel delivery, they are allobjectionable for one reason or another.

The object of my invention is to provide a port-controlled fuelinjection pump of the type and for the purpose described with simple andeffective means for producing a declining characteristic of fueldelivery, or in other words for decreasing the amount of fuel deliveredby each stroke of a pump plunger as the speed increases, the means forthis purpose being readily applicable to types of fuel injecting pumpsnow in use with little or no increase in the cost of their manufacture.Pumps of the type contemplated by my invention include a barrel portthat communicates with a source of fuel supply, and also with adischarge passage adapted to be connected to a discharge tube leading toan engine cylinder. Within the barrel there is a fuel-feeding plunger bythe usual cam shaft in timed relation with the cycle of the engine.Controlling the discharge passage of the barrel there is a valve whichis yieldingly pressed towards closed posiwhich may be reciprocated theabove-explained difference which is provided with a tion of the barrelthat tion and whose seat is formed upon a prolongais usually, althoughnot necessarily, a separate element.

To effect a ation of such a pump, I provide its barrel, between itsplunger and delivery valve, with a leakage passage for the escape fromthe barrel of a small amount of fuel, the amount increasing with theincrease of pump speed. Preferably the leakage'escape passagecommunicates with the source of fuel supply, as for example with a sumpsurrounding the barrel. The leakage escape passage is preferably quiteshallow to effect or promote laminar flow through it, while thedischarge line from the pump is substantially circular in cross sectionwhich results in turbulent flow through it. Discharge of fuel from thepump barrel under laminar flow varies as the first power of the pressureof the fuel, while discharge under turbulent fiow varies as the squarefoot of that pressure. Thus, as the pressure of the fuel in the barrelincreases consequent upon increased pump speed, more fuel will passthrough both the leakage passage and the discharge line, but theincrease through the leakage passage is relatively more than through thedischarge line because of between the variations of laminar andturbulent flow due to changes in pressure of the fluid. To furtherincrease the flow of fuel through the leakage passage as the pressure ofthe fuel in the barrel increases consequent upon increased pump speed,the leakage escape passage may be of variable cross section adapted toincrease with increasing fuel pressure.

The flow of fuel through the leakage escape passage may be made morepronounced by restricting the flow of fuel from the barrel into thedischarge line. This may be done by providing the pump with a throttlingorifice which may be variously located,-by limiting the lift of thedischarge valve, or by the construction of such valve.

The invention is illustrated in the accompanying drawing of which Fig. 1is a vertical central sectional view through a port-controlled fuelinjection pump; Fig. 2 a similar view through a like pump showingmodifications of construction; and Fig. 3 a vertical central sectionalview through the delivery valve of the pump showing a furthermodification of construction.

The pump illustrated in Fig. 1 includes a barrel l mounted in a casingor body 2 and provided with a reciprocable plunger 3. On the upperportion of the plunger there is a helix 4 of familiar constructionadapted, by being rotated declining characteristic in the operupon itsaxis, to control the efiective stroke of the plunger by placing thebarrel space above the plunger in communication with a spill passage 5.Fuel is supplied to the barrel through spill passage 5 and an inlet port5a. For thus adjusting the angular position of plunger 3, or in otherwords for rotating it upon its axis, there is a control rod 6 which isprovided with a rack I that meshes with a pinion 8 attached to a sleeve9 which is rotatably mounted upon barrel l and engages the lower end ofthe plunger.

Port 5a and spill passage 5 of the barrel communicate with a sump llformed in the pump body and which in turn has communication with asource of fuel supply, At the upper end of barrel I there is a deliveryvalve assembly including a bushing I2, which in effect is a prolongationof barrel I, having a seat at its upper end for receiving a dischargecontrolling valve l3 which is yleldingly pressed towards its closedposition by a spring l4 seated at its upper end in a valve holder l5that is attached to pump body 2.

In this embodiment of my invention the pump is provided with a leakageescape passage of variable cross section. To that end, annular springwashers I 6, of the Belleville or similar type, are placed between thelower end of valve holder l5 and an outwardly extending flange at thelower end of bushing l2 (the interior wall of which bushing overhangsthe wall of barrel I) and pump body 2 is provided with a channel 41extending from the space surrounding bushing l2 to sump H. Dependingupon the fuel pressure in the pump barrel, bushing I2 is elevated toform a shallow leakage escape passage l8 of variable cross-sectionalarea between the lower end of the bushing and the upper end of thebarrel.

In the embodiment of my invention illustrated in Fig. 2, a similarshallow leakage escape passage l8a, but of fixed cross-sectional area,is formed between barrel l and bushing l2 which are not movable withrelation to each other during the operation of the pump.

For throttling the discharge flow of fuel from the pump, and thereby tomake the declining delivery characteristic of fuel more pronounced byincreasing relatively the laminar flow of fuel that escapes through theleakage passage, delivery valve holder l5 may be provided with athrottling orifice 20, as shown in Fig. 1. As shown in Fig. 2, a similarthrottling of the discharge flow of the fuel may be effected byproviding valve I311 with a depending skirt 2| which fits loosely withinthe bore of bushing [2a. The upper portion of skirt 2| is provided witha peripheral groove 22 and with small openings 23 which place the groovein communication with the interior of the skirt. Fuel flows from thepump chamber between the exterior of skirt 2| and the bore of bushingl2a, and also through the interior of that skirt and holes 23, by whichrestricted passages the discharge flow of fuel is throttled.

The flow of discharge fluid may also be throttled by providing thedelivery valve with means for limiting the extent of its opening underfuel pressure. As shown in Fig. 3, this may be accomplished by providingthe upper end of bushing l2b with a stop in the form of a ring 25 whichthreadably engages the upper end of the bushing and is provided with aninwardly turned flange 26 that overhangs the top of valve 13b. Thethrottling thus produced by limiting the opening of the valve may ingthe position of ring 25.

In the operation of the fuel injection pump provided according to myinvention the angular position of the pump plunger is adjusted, asusual, to effect the desired feed of fuel depending upon the engineload. When the engine speed increases, and as a consequence thereof morefuel is supplied to the engine by reason of the increased speed ofreciprocation of the pump plunger, a portion of the fuel flows throughthe leakage escape passage to the source of fuel supply, this portionvarying with the increase in speed. In this way the feed of fuel has thedesired declining characteristic resulting in increased torque,elimination of or reduction in smoke in the exhaust, and better enginestability.

According to the provisions of the patent statutes I have explained theprinciple of my invention and have illustrated and described severalembodiments of it. However, I desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. A port-controlled injection pump for internal combustion engines ofthe Diesel type, comprising in combination a barrel provided with a portcommunicating with a source of fuel supply and with a discharge passage,a valve controlling flow of fuel through the discharge passage, and afuel feeding plunger reciprocable in said barrel, the barrel beingprovided with a mechanically-controlled spill passage and also with aleakage escape passage having its inlet positioned between said valveand plunger and being in communication with the source of fuel supply,flow of fuel through said leakage escape passage being effected andcontrolled solely by the pressure applied to the fuel by the pump.

2. A port-controlled injection pump for internal combustion engines ofthe Diesel type, comprising in combination a barrel provided with a portcommunicating with a source of fuel supply and with a discharge passage,a valve controlling flow of fuel through the discharge passage, and afuel feeding plunger reciprocable in said barrel, the barrel beingprovided with a mechanically-controlled spill passage and also with ashallow leakage escape passage having its inlet between said valve andplunger and being formed to promote laminar flow of fuel from thebarrel, flow of fuel through said leakage escape passage being effectedand controlled solely by the pressure applied to the fuel by the pump.

3. A port-controlled injection pump for internal combustion engines ofthe Diesel type, comprising in combination a barrel provided with a portcommunicating with a source of fuel supply and with a discharge passage,a valve controlling flow. of fuel through the discharge passage, and afuel feeding plunger reciprocable in said barrel, the barrel beingprovided with a mechanically-controlled spill passage and also with ashallow leakage escape passage of fixed cross-sectional area having itsinlet between said valve and plunger and formed to promote laminar flowof fuel from the barrel, flow of fuel through said leakage escapepassage being effected and controlled solely by the pressure applied tothe fuel by the pump.

4. A port-controlled injection pump for internal combustion engines ofthe Diesel type,

be varied by adjustwith a shallow leakage escape comprising incombination a barrel provided with a port communicating with a source offuel supply and. with a discharge passage, a valve controlling flow offuel through the discharge passage, and a fuel feeding plungerreciprocable in said barrel, the barrel being provided with amechanically-controlled spill passage and also passage of variablecross-sectional area having its inlet between said valve and plunger andbeing formed to promote laminar flow of fuel from the barrel, flow offuel through said leakage escape passage being effected and controlledsolely by the pressure applied to the fuel by the pump.

5. A port-controlled injection pump for internal combustion engines ofthe Diesel type, comprising in combination a barrel provided with a portcommunicating with a source of fuel supply and with a discharge passage,a valve controlling flow of f el through the discharge passage, a fuelfeeding plunger reciprocable in said barrel, the barrel being providedwith a shallow leakage escape passage having its inlet between saidvalve and plunger and being formed to promote laminar flow of fuel fromthe barrel, and means beyond said escape passage for throttling the flowof fuel.

6. A port-controlled inlection pump for internal combustion engines ofthe Diesel type. comprising in combination a barrel provided with a portcommunicating with a source of fuel supply and with a-discharge passage,a valve controlling flow of fuel through the discharge passage, a fuelfeeding plunger reciprocable in said barrel, the barrel being providedwith a shallow leakage escape passage having. its inlet between saidvalve to promote laminar flow of fuel from the barrel, and a restrictedorifice beyond said escape passage for thr 'ttling the flow of fuel.

I PAUL H. SCHWEITZER.

and plunger and beingformed

